The present invention relates to a scroll fluid machine suitable for use as an air compressor, a vacuum pump, etc. by way of example.
In general, a scroll fluid machine includes a fixed scroll and an orbiting scroll which is positioned to face the fixed scroll. The fixed scroll and the orbiting scroll each have a disk-shaped end plate and a wrap portion which projects axially from the end plate. The wrap portion is wound spirally from the radially inner side toward the radially outer side of the end plate. Thus, the fixed scroll and the orbiting scroll define a plurality of compression chambers by overlapping of their wrap portions.
In the scroll fluid machine, the orbiting scroll is driven by a driveshaft to perform an orbiting motion with respect to the fixed scroll with a predetermined orbiting radius, thereby sucking a fluid, e.g. a gas, from a suction opening provided in a radially outer part of the fixed scroll, and successively compressing the fluid in the compression chambers. Finally, the compressed fluid is discharged to the outside from a discharge opening provided in a radially inner part of the fixed scroll.
There is known a scroll fluid machine having a plurality of projections on peripheral surfaces of wrap portions to reduce a gap between the wrap portions, and thereby increase a degree of hermeticity of compression chambers, and improve a compression efficiency, as described, for example, in Japanese Patent Application Unexamined Publication (KOKAI) No. 2005-76517. The plurality of projections are spaced apart in a winding direction (spiral direction), on the peripheral surfaces of the wrap portions, so as to project in a radial direction, relative to their surrounding area, from the peripheral surfaces of the wrap portions.
It is to be noted that the above-described scroll fluid machine of the related art has a plurality of axially extending projections on the peripheral surfaces of the wrap portions to reduce an amount of compressed fluid leaking through mutually opposing wrap portions, so as to increase a degree of hermeticity of the compression chambers. However, due to errors in dimensions, assembly, or the like of the compressor, the scroll fluid machine of the related art may suffer galling and so on when the projections make contact with the peripheral surface of the mating wrap portion. This leads to further power loss, more noise, and so on.
There is also known a structure that is provided with a soft resin film on a peripheral surface of a wrap portion to fit the resin film with the projections, thereby preventing galling and so on. In this case, however, if the resin film is too thick, the entire peripheral surface of the wrap portion makes contact with the resin film, which leads to further power loss, more noise, and so on. On the other hand, if the resin film is too thin, the projections do not make contact with the resin film, causing a problem of reducing the effect of the projections and increasing the degree of hermeticity of the compression chambers.